Digital video switching apparatus

ABSTRACT

A digital video switching apparatus is disclosed in which a 4:2:2 digital video signal and a 4:4:4 digital video signal supplied at input terminals are selected by switching by a matrix switcher unit in order to transmit the 4:2:2 digital video signal to a first signal processing unit and in order to transmit the 4:2:2 digital video signal to a second signal processing unit. The first signal processing unit converts the 4:4:4 digital video signal into the 4:2:2 digital video signal by signal processing, such as color correction. The second signal processing unit performs signal processing, such as mixing or wiping, on the 4:2:2 digital video signal and the 4:2:2 digital video signal directly supplied from the matrix switcher unit, in order to output the processed 4:2:2 digital video signal. The input terminals may be simultaneously employed as the input terminals for the 4:2:2 digital video signal and the input terminals for the 4:4:4 digital video signal, while there is no necessity of providing input terminals dedicated to the 4:4:4 digital video signal. On the other hand, a device for supplying the 4:2:2 digital video signal or a device for supplying the 4:4:4 digital video signal may be connected to the input terminals so that the 4:2:2 digital video signal and the 4:4:4 digital video signal will be arbitrarily switched and selected by the matrix switcher unit or otherwise employed in combination.

BACKGROUND OF THE INVENTION

This invention relates to a digital video switching apparatus (switcher)for selecting and outputting a desired digital video signal from among aplurality of input digital video signals. More particularly, it relatesto a digital video switcher handling both the digital video signalhaving the data rate for luminance and chrominance signals of 4:2:2 andthe digital video signal having the data rate for luminance andchrominance signals of 4:4:4.

There has generally been known a digital video switcher handling aD1-format digital video signal having the data rate for the luminancesignal Y and the chrominance signals U and V of 4:2:2, referred toherein as the 4:2:2 digital video signal. It is not possible with thistype of the digital video switcher to process a digital video signalhaving the Y:U:V ratio of 4:4:4, referred to herein as the 4:4:4 digitalvideo signal, because its internal signal processing hardware, such as awipe or a chroma key, has the capability of processing only the 4:2:2video signal. It is however desired of such digital video switcher to becapable of processing the 4:4:4 digital video signal as the source videosignal as well.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a digital videoswitching apparatus capable of handling both a digital video signalhaving a data rate for the luminance signal and the chrominance signalof 4:4:4 and a digital video signal having a data rate for the luminancesignal and the chrominance signal of 4:2:2.

It is another object of the present invention to provide a digital videoswitching apparatus in which there is no necessity of changing thewiring in case of a source apparatus being changed over and in whichfacilitated control of the matrix switcher unit may be achieved.

According to the present invention, there is provided a digital videoswitching apparatus having a matrix switcher unit having a plurality ofinput buses respectively connected to a plurality of input terminals anda plurality of output buses selectively connected to respective ones ofthe input buses, and a first signal processing unit connected to two ofthe output buses selectively connected to two of the input busessupplied with a 4:2:2 digital video signal and a 0:2:2 digital videosignal together making up a 4:4:4 digital video signal. The first signalprocessing unit performs signal processing on the 4:4:4 digital videosignal at a rate of 4:4:4 for outputting a corresponding 4:2:2 digitalvideo signal. The video switching apparatus also has a second signalprocessing unit connected to one of the output buses selectivelyconnected to one of the input buses supplied with the 4:2:2 digitalvideo signal and to the first signal processing unit. The second signalprocessing unit performs signal processing on the 4:2:2 digital videosignal supplied via the input bus and on the 4:2:2 digital video signalsupplied from the first signal processing unit for outputting acorresponding 4:2:2 digital video signal.

The first signal processing unit may include a chroma key for generatinga 4:2:2 foreground signal and a 4:0:0 key signal from the 4:2:2 digitalvideo signal and the 0:2:2 digital video signal.

The first signal processing unit may include a color corrector forgenerating a 4:2:2 digital video signal from the 4:2:2 digital videosignal and the 0:2:2 digital video signal.

According to the present invention, the 4:4:4 video signal supplied viaat least two of plural output buses of the matrix switcher unitconnected to the input terminals is processed by a first signalprocessing unit to produce a 4:2:2 video signal which is fed to thesecond signal processing unit. The second signal processing unitprocesses a 4:2:2 video signal supplied via output buses of the matrixswitcher unit other than those connected to the first signal processingunit, and the 4:2:2 video signal supplied from the first signalprocessing unit, in order to output a 4:2:2 video signal.

With the digital video switching apparatus according to the presentinvention, the input terminals can be used simultaneously for receivingthe 4:2:2 video signal and the 4:4:4 video signal, while there is nonecessity of providing input terminals dedicated to the 4:4:4 videosignal. On the other hand, the device for supplying the 4:2:2 videosignal and the device for supplying the 4:4:4 video signal may beconnected to the input terminals so that the 4:4:4 video signal can bearbitrarily switched to the 4:2:2 video signal or vice versa by thematrix switcher unit. Alternatively, the two video signals can be usedin combination. In addition, since the matrix switcher unit for inputselection is enclosed in the digital video switching apparatus, there isno necessity of controlling the external pre-matrix for input selectionsuch that control may be achieved positively by a simplified controlsystem. Since the pre-matrix may be eliminated, the apparatus may beimproved in operability and reliability, while its production cost maybe lowered.

Thus the present invention provides a digital video switching apparatuswhich is high in versatility and can be controlled easily without thenecessity of providing input terminals dedicated to the 4:4:4 videosignal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a digital video switcher havingpertinence to the present invention.

FIG. 2 is a block diagram showing another digital video switcher havingpertinence to the present invention.

FIG. 3 is a block diagram showing a digital video switcher according tothe present invention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

Before proceeding to description of the present invention, a digitalvideo switcher having pertinence to the present invention is explainedby referring to FIG. 1.

A digital video switcher 20 shown in FIG. 1 is a digital video switcherfor the 4:2:2 video signal. This digital video switcher 20 includes achroma key processing unit 21 for processing the 4:4:4 video signal anda color corrector 22. That is, in addition to primary input terminals T₁to T₃₂ connected via a matrix switcher unit 23 to an effect switcher 24for the 4:2:2 video signal, input terminals Ts₁ and Ts₂ dedicated to the4:4:4 video signal are provided and connected to a chroma key processingunit 21 and to a color corrector 22 for processing the 4:4:4 videosignal. The 4:4:4 video signal supplied to the input terminals T_(s1)and T_(s2) dedicated to the 4:4:4 video signal is converted via thechroma key processing unit 21 and the color corrector 22 into the 4:2:2video signal which then enters an effect switcher unit 24 for the 4:2:2video signal as the 4:2:2 video signal. The effect switcher unit 24processes the desired 4:2:2 video signal, supplied thereto via thematrix switcher unit 23 from the primary input terminals T₁ to T₃₂, withmixing or wiping etc., and outputs the processed 4:2:2 video signal.

It is only the equipment connected to the input terminals T_(s1) andT_(s2) that can be employed as being connected to the chroma keyprocessing unit 21 and the color corrector 22. Thus, rewiring isrequired when changing over the source device supplying the 4:4:4 videosignal from e.g., a telecine device to a camera.

Thus the digital video switcher 20, shown in FIG. 1, provided with theinput terminals T_(s1) and T_(s2) dedicated to the 4:4:4 video signal,lacks in versatility, and is in need of re-wiring in case of changing asource device for the 4:4:4 video signal from e.g., a telecine device toa camera.

For overcoming such inconvenience, it may be envisaged to provide apre-matrix 30 externally of the digital video switcher 20 for selectinginputs outside of the digital video switcher 20, as shown in FIG. 2.Although the re-wiring is unnecessary with the arrangement of FIG. 2,the control system becomes highly complex because the switching of theinputs and outputs in the pre-matrix 30 provided outside of the digitalvideo switcher 20 needs to be performed under control by the digitalvideo switcher 20. That is, since the control signal for switching needsto be transmitted from the digital video switcher 20 to the pre-matrix30, there is produced a delay in the switching timing, and hence itbecomes necessary to design the control system so that such delay in thechangeover timing will be taken into account.

Thus the present invention provides a digital video switcher 10 in whichthe pre-matrix 30 as shown in FIG. 2 is not employed and in which boththe 4:2:2 digital video signal and the 4:4:4 digital video signal may beprocessed without providing dedicated input terminals for the 4:4:4digital video signal.

FIG. 3 shows such digital video switcher 10 according to the presentinvention.

The digital video switcher 10 is adapted to handle both the 4:2:2digital video signal, that is the digital video signal having the datarate for the luminance signal and the chrominance signal of 4:2:2, andthe 4:4:4 digital video signal, that is the digital video signal havingthe data rate for the luminance signal and the chrominance signal of4:4:4, and includes primary input terminals T₁ to T₃₂ supplied with the4:2:2 video signal and the 4:4:4 digital video signal. To these primaryinput terminals T₁ to T₃₂ are connected a first signal processor 12 anda second signal processor 13 via a matrix switcher unit 11.

At least two of plural output buses of a matrix switcher unit 11 areconnected to a first signal processor 12 adapted for processing the4:4:4 video signal for outputting the 4:2:2 video signal. The firstsignal processor 12 of the present embodiment includes a chroma keyprocessing unit 12A and a color corrector 12B respectively connected totwo output buses and other two output buses of the matrix switcher unit11.

That is, the 4:4:4 video signal is supplied as e.g., a 4:2:2 videosignal and a 0:2:2 video signal to two of the primary input terminals T₁to T₃₂, so as to enter the chroma key processing unit 12A and the colorcorrector 12B of the first signal processing unit 12 via two of theinput buses of the matrix switcher unit 11 associated with the two ofthe input terminals T₁ to T₃₂ and via two of output buses of the matrixswitcher unit 11 respectively connected to the two input buses.

The chrome key processing unit 12A processes the 4:4:4 video signal,supplied thereto from the primary input terminals T₁ to T₃₂ via thematrix switcher unit 11, at a data rate of 4:4:4, and transmits the4:2:2 foreground signal and the 4:0:0 key signal to a second signalprocessing unit 13. The color corrector 12B performs color correction,at a data rate of 4:4:4, on the 4:4:4 video signal supplied from theprimary input terminals T₁ to T₃₂ via the matrix switcher unit 11, andconverts the corrected 4:4:4 video signal into the 4:2:2 video signalwhich is supplied to the second signal processor unit 13. The chroma keyprocessing unit 12A or the color corrector 12B extracts specified colorcomponents, by taking advantage of the color difference, and generates aso-called key signal. The chroma key processing unit 12A performsprocessing at a data rate of 4:4:4 for generating the chroma keyforeground signal and the key signal from the 4:4:4 video signal havingthe broad bandwidth of the color signal. In this manner, a highprecision key signal can be generated which enables extraction of a finepicture pattern. By performing color extinction processing at the datarate of 4:4:4 and subsequently generating the 4:2:2 foreground signal,it becomes possible to reduce the effects of distortion by non-linearprocessing or aliasing in order to produce the foreground signal of highpicture quality.

The 4:2:2 video signal supplied from the primary input terminals T₁ toT₃₂ and the 4:4:4 video signal supplied via the primary input terminalsT₁ to T₃₂ and the matrix switcher unit 11 and subsequently processed bythe first signal processing unit 12 are processed by the second signalprocessor 13 with mixing or wiping for outputting the processed 4:2:2video signal.

The matrix switcher unit 11 has re-entry signal paths in order to permitoutputs of the chroma key processing unit 12A or the color corrector 12Bto be used as other inputs to the second signal processing unit 13 or anauxiliary bus.

With the above-described digital video switcher 10, the primary inputterminals T₁ to T₃₂ are connected via the matrix switcher unit 11 to thefirst signal processor 12 for the 4:4:4 video signal and to the secondsignal processor 13 for the 4:2:2 video signal, so that any of theprimary input terminals T₁ to T₃₂ may be used as input terminals for the4:4:4 video signal. Consequently, there is no necessity of providinginput terminals dedicated to the 4:4:4 video signal. On the other hand,the device for supplying the 4:2:2 video signal or the device forsupplying the 4:4:4 video signal may be connected to the primary inputterminals T₁ to T₃₂ for optionally switching the 4:4:4 video signal tothe 4:2:2 video signal or vice versa or employing the two video signalsin combination.

The operation of the matrix switcher unit 11 and the first and secondsignal processing units 12, 13 is controlled by a control unit, notshown. Since the matrix switcher unit 11 for input selection is enclosedin the present digital video switcher 10, there is no necessity ofcontrolling the pre-matrix for external input selection and hencepositive control may be realized by a simplified control system. Sincethe pre-matrix is not required, the digital video switcher is simplifiedin construction and low in production cost, while being excellent inoperability or reliability.

Although only the 4:4:4 digital video signal is adapted to enter thefirst signal processing unit 12A and the color corrector 12B of thefirst signal processing unit 12 shown in FIG. 3, the 4:2:2 digital videosignal may also be adapted to enter the unit 12A and the color corrector12B selectively. In such case, the input 4:2:2 digital video signal maybe converted by up-rate conversion into the 4:4:4 digital video signalfor processing by chroma key generation and color correction.

What is claimed is:
 1. A digital video switching apparatus comprising:amatrix switcher unit having a plurality of input buses respectivelyconnected to a plurality of input terminals and a plurality of outputbuses selectively connected to respective ones of the input buses; afirst signal processing unit connected to two of said output busesselectively connected to two of said input buses supplied with a 4:2:2digital video signal and a 0:2:2 digital video signal together making upa 4:4:4 digital video signal, said first signal processing unitperforming signal processing on said 4:4:4 digital video signal at arate of 4:4:4 for outputting a corresponding 4:2:2 digital video signaland a second signal processing unit connected to one of the output busesselectively connected to one of the input buses supplied with the 4:2:2digital video signal and to said first signal processing unit, saidsecond signal processing unit performing signal processing on the 4:2:2digital video signal supplied via said input bus and on the 4:2:2digital video signal supplied from the first signal processing unit foroutputting a corresponding 4:2:2 digital video signal.
 2. The digitalvideo switching apparatus as claimed in claim 1, wherein said firstsignal processing unit comprises a chroma key generator for generating a4:2:2 foreground signal and a 4:0:0 key signal from said 4:2:2 digitalvideo signal and said 0:2:2 digital video signal.
 3. The digital videoswitching apparatus as claimed in claim 1, wherein said first signalprocessing unit comprises a color corrector for generating a 4:2:2digital video signal from said 4:2:2 digital video signal and said 0:2:2digital video signal.